CN1568261A

CN1568261A - Residue removal from nozzle guard for ink jet printhead

Info

Publication number: CN1568261A
Application number: CNA028201205A
Authority: CN
Inventors: 卡·西尔弗布鲁克
Original assignee: Silverbrook Research Pty Ltd
Current assignee: Silverbrook Research Pty Ltd
Priority date: 2001-08-31
Filing date: 2002-08-21
Publication date: 2005-01-19
Anticipated expiration: 2022-08-21
Also published as: EP1432586B1; IL160634A0; US20090237447A1; DE60214742D1; US7556344B2; US20050243123A1; ZA200401821B; US6412904B1; EP1432586A1; JP2005500193A; US6953236B2; US7152943B2; EP1432586A4; CA2458602A1; CN1270899C; JP4154331B2; US20050073549A1; AU2002356076B2; US20070064044A1; ATE339317T1

Abstract

A nozzle guard (80) for an ink jet printer printhead with an array (14) of nozzles (10). The nozzle guard (80) has an array of apertures (84) individually corresponding to the nozzle array (14). The ink droplets are ejected through the apertures (84) and onto the media to be printed. A wiper blade (143) sweeps dust and residual ink (144) stuck to the exterior surface (142) of the nozzle guard (82) characterized in that the exterior surface (142) has a recess (146) individually associated with each of the apertures (86) for preventing residual matter (144) carried by the wiper blade (143) from lodging within the aperture (84).

Description

Nozzle protector of ink-jet printing head capable of removing residual substance

Technical Field

The present invention relates to digital printers, and more particularly to ink jet printers.

Background

Ink jet printers are a well known and widely used form of print media production. The colorant, typically ink, is delivered to a microprocessor controlled nozzle array on the printhead. As the printhead passes over the print medium, colorant is ejected from the nozzle array to produce a printed image on the media substrate.

The performance of a printer depends on factors such as running cost, print quality, running speed, and ease of operation. In general, the frequency and velocity of individual ink drops ejected from a nozzle can affect these performance parameters.

Recently, micro-electro-mechanical systems (MEMS) technology has been used to fabricate nozzle arrays with sub-micron thickness mechanical structures. This enables the manufacture of a spray that can be rapidly ejected in picoliters (10 ×)^-12Liter) ink drop.

While the microstructure of these printheads can provide high speed and good print quality at relatively low cost, their size makes the nozzles extremely fragile and susceptible to damage from the slightest contact by fingers, dust or media substrates. This makes such a printhead impractical in most practical applications where a certain robustness of the printhead is required. Moreover, a damaged nozzle may not be able to eject the colorant delivered to it. The colorant accumulates and forms a bead on the exterior of the nozzle, which may interfere with the ejection of colorant from surrounding nozzles and/or the damaged nozzle may leak colorant directly onto the media substrate. Both of these conditions are detrimental to print quality.

For this purpose, an aperture guard may be mounted on the nozzle to protect them from damaging contact. Ink ejected from the nozzles is ejected through the apertures onto a print sheet or other print substrate. However, in order to effectively protect the nozzle, the aperture needs to be as small as possible to maximally restrict intrusion of foreign particles while allowing the ink droplets to pass therethrough. Ideally, each nozzle would eject ink through an aperture in their own guard.

Typically, the pores in the guard are extremely small so they are prone to clogging. Therefore, it is often desirable to keep the outer surfaces of the nozzle guard clean, especially in environments with relatively high levels of dust or other airborne particles. The outer surface of the guard is periodically cleaned with a wiper blade to remove dust or ink residue, which is a convenient way to achieve the above-mentioned desire. However, the residual substances on the blade generally collect on the outer edge, particularly on the portion of the edge facing the direction of travel of the blade. The build-up of residual material is less easily removed by the wiper blade and will quickly clog the pores.

Disclosure of Invention

Accordingly, the present invention provides an apertured nozzle guard for an ink jet printer printhead, the printhead including an array of nozzles for ejecting colorant onto a print substrate; wherein,

the nozzle guard is adapted to be positioned on the printhead such that the nozzle guard extends over the exterior of the nozzle to prevent damaging contact with the nozzle while allowing colorant ejected from the nozzle to pass through the aperture and onto a print substrate; the nozzle guard includes:

an outer surface, the outer surface facing the media in operation;

the outer surface is configured to engage a wiper blade that periodically cleans the surface to remove residual material; wherein,

the outer surface has a groove that individually mates with each aperture to prevent the wiper blade from engaging the outer surface immediately adjacent the aperture.

In this specification, the term "nozzle" is to be understood as an element defining an opening, not the opening itself.

Preferably, the outer surface further comprises a guide ridge in each groove, the guide ridge being arranged to engage the wiper blade before the wiper blade passes over the aperture which mates with the groove. In one convenient form of implementation, the guide ridge is arcuate and is positioned relative to the direction of travel of the wiper blade to direct residual material away from the aperture and to the edge of the recess.

The nozzle guard may also include a fluid inlet for directing fluid over the nozzle array and out through the channel to prevent the accumulation of foreign particles on the nozzle array.

The nozzle guard may include a pair of integrally formed and spaced apart support members, one of which is disposed at each end of the nozzle guard.

In this embodiment, the fluid inlet may be provided on one of the support elements.

It will be appreciated that as air is directed from the openings over the nozzle array and out of the channels, the accumulation of foreign particles on the nozzle array is prevented.

The fluid inlet may be provided in a support element remote from the connection pads of the nozzle array.

In order to optimize the effectiveness of the wiper blade, the outer surface is planar except for the grooves and the guide ridges. By making the guard from silicon, its coefficient of thermal expansion substantially matches that of the nozzle array. This will help prevent misalignment of the array of apertures in the guard with the array of nozzles. The use of silicon also allows the shields to be precisely micro-machined with MEMS technology. Moreover, silicon is very strong and substantially non-deformable.

Drawings

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG.1 is a perspective view of a nozzle assembly of an inkjet printhead;

FIGS. 2-4 are perspective views illustrating the operation of the nozzle assembly of FIG. 1;

FIG.5 is a perspective view of the nozzle array;

FIG. 6 is an enlarged partial view of the array of FIG. 5;

FIG.7 is a perspective view of an ink jet print head including a nozzle guard;

FIG.7a is a partial cross-sectional view of the inkjet printhead and nozzle guard cleaned by a wiper blade of FIG. 7;

FIG.7b shows a partial cross-sectional view of a nozzle guard of the present invention;

FIG.7c shows a plan view of the outer surface of the nozzle guard of FIG.7 b;

FIGS. 8 a-8 r are perspective views illustrating steps in the manufacture of a nozzle assembly for an ink jet printhead;

FIGS. 9 a-9 r show side cross-sectional views of the manufacturing steps;

FIGS. 10 a-10 k show mask layouts for use in different steps in the manufacturing process;

11 a-11 c are perspective views illustrating the operation of the nozzle assembly manufactured according to the method of FIGS. 8 and 9; and

fig.12 a-12 c are cross-sectional side views illustrating operation of a nozzle assembly manufactured according to the method of fig. 8 and 9.

Detailed Description

Referring initially to FIG.1, a nozzle assembly of the present invention is generally indicated by reference numeral 10. An ink jet print head has a plurality of nozzle assemblies 10 arranged on a silicon substrate 16 in an array 14 (shown in figures 5 and 6). The array 14 will be described in more detail below.

The nozzle assembly 10 includes a silicon substrate 16 on which a dielectric layer 18 is deposited. A CMOS passivation layer 20 is deposited over dielectric layer 18.

Each nozzle assembly 10 includes a nozzle 22 defining a nozzle opening 24, a connecting member in the form of a lever arm 26, and an actuator 28. The actuator 28 is connected to the nozzle 22 by a lever arm 26.

As shown in greater detail in fig. 2-4, the nozzle 22 includes a crown 30 with a skirt portion 32 depending from the crown 30. The skirt portion 32 forms a part of the peripheral wall of the nozzle chamber 34. The nozzle opening 24 is in fluid communication with the nozzle chamber 34. Note that the nozzle opening 24 is surrounded by a raised rim 36, which raised rim 36 is intended to "dig" into a meniscus 38 (fig. 2) of a body of ink 40 in the nozzle chamber 34.

An ink inlet aperture 42 (best shown in fig. 6) is defined in a floor 46 of the nozzle chamber 34. The liquid in the pores 42 is in fluid communication with an ink feed channel 48 defined by the substrate 16.

A wall portion 50 defines the aperture 42 and extends upwardly from the floor 46. As described above, the skirt portion 32 of the nozzle 22 defines a first portion of the peripheral wall of the nozzle chamber 34, while the wall portion 50 defines a second portion of the peripheral wall of the nozzle chamber 34.

The free end of the wall 50 has an inwardly directed lip 52 which acts as a liquid seal to prevent spillage of ink as the nozzle 22 is moved, as will be described in more detail below. It will be noted that because of the viscosity of the ink 40 and the small size of the space between the lip 52 and the skirt portion 32, the inwardly directed lip 52 and surface tension act as a seal which effectively prevents ink from escaping from the nozzle chamber 34.

Actuator 28 is a thermal bend actuator and is attached to a spring 54 that extends upwardly from substrate 16, or more specifically from CMOS passivation layer 20. The spring 54 is mounted on a conductive pad 56 which forms an electrical connection with the actuator 28.

The actuator 28 includes a first active beam 58 disposed on a second passive beam 60. In a preferred embodiment, the two beams 58 and 60 are, or include, a conductive ceramic material such as titanium nitride (TiN).

Both beams 58 and 60 have a first end attached to leaf 54 and their opposite ends connected to lever arm 26. When current is generated across the active beam 58, it causes the beam 58 to thermally expand. Since no current flows in the passive beam 60, it does not expand at the same rate, which creates a bending moment that causes the lever arm 26, along with the nozzle 22, to be pushed downward toward the substrate 16, as shown in FIG. 3. This causes ink to be ejected through the nozzle opening 24, as shown at 62. When the heat source is removed from the active beam 58, i.e., the current is cut off, the nozzle 22 returns to its rest position, as shown in FIG. 4. When the nozzle 22 returns to its rest position, as shown at 66 in fig. 4, a drop 64 is formed due to the break-off at the constriction of the drop. The ink drops 64 are then delivered to a print medium such as paper. As a result of the formation of the ink drop 64, a "concave" meniscus is formed, as shown at 68 in FIG. 4. The "concave" meniscus 68 causes ink 40 to flow into nozzle chamber 34, thereby forming a new meniscus 38 (shown in FIG. 2) ready for the next drop to be ejected from nozzle assembly 10.

The nozzle array 14 will now be described in detail in connection with fig.5 and 6. The array 14 is described for a four color printhead. Thus, the array 14 includes four nozzle assembly sets 70, one for each color. Each group 70 has nozzle assemblies 10 arranged in two

rows

72 and 74. One of the sets 70 is shown in greater detail in fig. 6.

To facilitate close-packed arrangement of the nozzle assemblies 10 in the

rows

72 and 74, the nozzle assemblies 10 in the row 74 are offset or staggered relative to the nozzle assemblies 10 in the row 72. Moreover, the nozzle assemblies 10 in the row 72 are sufficiently spaced apart from one another to enable the lever arms 26 of the nozzle assemblies 10 in the row 74 to pass between adjacent nozzles 22 of the assemblies 10 in the row 72. Note that each nozzle assembly 10 is substantially dumbbell-shaped so that the nozzles 22 in row 72 are nested between the nozzles 22 and the actuator 28 of an adjacent nozzle assembly 10 in row 74.

Moreover, to facilitate close packing of the

rows

72 and 74 of nozzles 22, each nozzle 22 is substantially hexagonal in shape.

It will be appreciated by those skilled in the art that as the nozzle 22 is moved toward the substrate 16 in operation, ink is ejected slightly off of perpendicular due to the slight angle of the nozzle opening 24 relative to the nozzle chamber 34. An advantage of the arrangement shown in fig.5 and 6 is that the actuators 28 of the nozzle assemblies 10 in

rows

72 and 74 extend in the same direction to one side of

rows

72 and 74. The ink ejected from the nozzles 22 in the row 72 and the ink ejected from the nozzles 22 in the row 74 are therefore offset from each other by the same angle, resulting in improved print quality.

Also, as shown in FIG.5, the substrate 16 has connection pads 76 mounted thereon, the connection pads 76 being electrically connected to the actuators 28 of the nozzle assembly 10 by conductive pads 56. These electrical connections are formed through CMOS layers (not shown).

Figure 7 shows a nozzle array and a nozzle guard. For each of the above figures, like reference numerals refer to like parts, unless otherwise specified.

A nozzle guard 80 is mounted on the silicon substrate 16 of the array 14. The nozzle guard 80 includes a shield 82, the shield 82 having a plurality of apertures 84 defined therethrough. The apertures 84 are aligned with the nozzle openings 24 of the nozzle assemblies 10 of the array 14 so that when ink is ejected from any of the nozzle openings 24, the ink can pass through the associated channel before being ejected onto a print medium.

In environments with relatively high levels of dust or other airborne particles, the pores 84 will become clogged. Also, the outer surface of the nozzle guard 80 may collect ink that leaks from a damaged nozzle. As shown in fig.7a, it is advantageous to use a wiper 143 to periodically clean the residual material 144 from the outer surface 142. Unfortunately, the residue 144 on the blade 143 often clogs the outer edges of the aperture 84, especially the portion of the edge facing the direction of travel 145 of the blade. The residual material 144 thus accumulated is less easily removed by the wiper 143 and quickly blocks the aperture 84.

As shown in fig.7b, the present invention provides a groove in the outer surface 142 surrounding each aperture 84. The wiper 143 can now pass over the aperture 84 so that the collected residue 144 does not collect in the outer edge. As a further safeguard, each groove 146 has a guide ridge 147. As shown in fig.7c, the guide ridge 147 directly engages the wiper blade 143 before the wiper blade 143 passes over the aperture 84. The guide ridge 147 clears the wiper blade 143 of some of the residual material 144 to further reduce the likelihood of the residual material 144 falling into the apertures 84. The guide ridge 147 is arcuate with its surface facing the direction of travel 145 of the wiper blade 143 to direct the accumulated residual material 144 away from the aperture 84 to the edge of the groove 146.

The guard 80 is silicon so that it has sufficient strength and rigidity to protect the nozzle array 14 from damage due to paper, dirt, or contact by a user's fingers. By forming the shield from silicon, its coefficient of thermal expansion substantially matches that of the nozzle array. This is intended to prevent the apertures 84 in the shield 82 from becoming misaligned with the nozzle array 14 when the temperature of the printhead is raised to its normal operating temperature. Silicon is also suitable for accurate micromachining using MEMS techniques, which will be discussed in detail below with respect to the fabrication of the nozzle assembly 10.

The shield 82 is mounted in spaced relation to the nozzle assembly 10 by an arm or post 86. One of the posts 86 has an air inlet 88 defined therein.

During operation of the printer, the array 14 is actuated and air enters through the inlet 88 and is forced through the apertures 84 along with the ink flowing through the apertures 84.

When air is flushed through the aperture 84 at a different velocity than the ink drops 64, the ink is not entrained in the air. For example, the ink droplets 64 are ejected from the nozzle 22 at a velocity of about 3 m/s. Air enters through the apertures 84 at a velocity of about 1 m/s.

The purpose of the air is to keep the pores 84 free of foreign particles. As mentioned above, there is a risk that these foreign particles, such as dust particles, may fall onto the nozzle assembly 10 adversely affecting its operation. This problem can be avoided by providing an air inlet 88 in the nozzle guard 80.

Referring now to fig. 8-10, a method of manufacturing the nozzle assembly 10 will be described.

Starting with a silicon substrate or wafer 16, a dielectric layer 18 is deposited on the surface of the wafer 16. The dielectric layer 18 is in the form of about 1.5 micron CVD oxide. Resist is spun on layer 18 and layer 18 is exposed to mask 100 and then developed.

After development, layer 18 is plasma etched onto silicon layer 16. The resist layer is then stripped and the layer 18 cleaned. This step defines the ink feed aperture 42.

In fig. 8b, about 0.8 microns of aluminum 102 is deposited on layer 18. Resist is spun on and the aluminum 102 is exposed to a mask 104 and developed. The aluminum 102 is plasma etched to the oxide layer 18, the resist is stripped and the device is cleaned. This step provides the connection pads and interconnects to the ink ejection actuators 28. The interconnect leads to the NMOS drive transistors and the power plane with the interconnect in the CMOS layer (not shown).

About 0.5 micron nitrided PECVD is deposited as the CMOS passivation layer 20. Resist is spun on and the layer 20 is exposed to a mask 106, where it is thereafter developed. After development, the nitride is plasma etched into the silicon layer 16 in the region of the aluminum layer 102 and the inlet aperture 42. The resist layer was stripped and the device cleaned.

A sacrificial layer 108 is spin coated over the layer 20. Layer 108 is 6 microns of photosensitive polyimide or about 4 microns of high temperature resist. Layer 108 is soft baked and then exposed to mask 110 and thereafter developed. Then, the layer 108 is hard-baked at 400 ℃ for one hour in the case where the layer 108 is made of polyimide, or at 300 ℃ or more in the case where the layer 108 is a high-temperature resist. It should be noted that the mask 110 is designed in the drawing in consideration of pattern-dependent distortion of the polyimide layer 108 due to shrinkage.

In a next step, shown in fig. 8e, a second sacrificial layer 112 is applied. Layer 112 is either a spin-on, 2 micron photosensitive polyimide or a high temperature resist of about 1.3 microns. Layer 112 is soft baked and then exposed to mask 114. After exposure to mask 114, layer 112 is developed. In the case where layer 112 is a polyimide, layer 112 is hard baked at 400 deg.C for about one hour. In the case where layer 112 is a resist, it is hard baked at a temperature above 300 c for about one hour.

A 0.2 micron multi-layer metal layer 116 is then deposited. Portions of this layer 116 form the passive beams 60 of the actuator 28.

Layer 116 is formed by sputtering 1,000 angstroms of titanium nitride (TiN) at a temperature around 300 c followed by 50 angstroms of tantalum nitride (TaN). Then, 1,000 angstroms of titanium nitride (TiN) is sputtered followed by 50 angstroms of tantalum nitride (TaN) and 1,000 angstroms of titanium nitride (TiN). Other materials that can be used in place of TiN are TiB₂、MoSi₂Or (Ti, Al) N.

Layer 116 is then exposed to mask 118, developed and plasma etched to layer 112, after which the resist layer applied over layer 116 is wet stripped, taking care not to remove cured

layers

108 or 112.

A third sacrificial layer 120 is applied by spin coating 4 microns of photosensitive polyimide or approximately 2.6 microns of high temperature resist. The layer 120 is soft baked and then exposed to a mask 122. The exposed layer is developed, followed by a hard bake. The layer 120 is hard baked at 400 c for about one hour in the case of polyimide, or above 300 c in the case where the layer 120 is made of resist.

A second multi-layer metal layer 124 is applied over layer 120. Layer 124 is the same composition and applied in the same manner as layer 116. It should be understood that both layer 116 and layer 124 are conductive layers.

Layer 124 is exposed to mask 126 and then developed. The layer 124 is plasma etched into the polyimide or resist layer 120, after which the resist applied over the layer 124 is wet stripped taking care not to remove the cured

layer

108, 112 or 120. It will be noted that the remaining portion of layer 124 defines active beam 58 of actuator 28.

A fourth sacrificial layer 128 is applied by spin coating 4 microns of photosensitive polyimide or approximately 2.6 microns of high temperature resist. Layer 128 is soft baked, exposed to mask 130, and then developed, leaving islands as shown in fig.9 k. The remaining portion of layer 128 is hard baked at 400 c for about one hour in the case of polyimide, or above 300 c in the case of resist.

A high young's modulus dielectric layer 132 is deposited as shown in figure 81. Layer 132 is comprised of about 1 micron of silicon nitride or aluminum oxide. The layer 132 is deposited at a temperature below the hard bake temperature of the

sacrificial layers

108, 112, 120, 128. The main characteristic requirements for the dielectric layer 132 are a high elastic modulus, chemical inertness and good adhesion to TiN.

A fifth sacrificial layer 134 is applied by spin coating 2 microns of photosensitive polyimide or about 1.3 microns of high temperature resist. Layer 134 is soft baked, exposed to mask 136, and then developed. The remaining portion of layer 134 is hard baked at 400 c for one hour in the case of polyimide, or above 300 c in the case of resist.

Dielectric layer 132 is plasma etched to sacrificial layer 128 taking care not to remove any sacrificial layer 134.

This step defines nozzle opening 24, lever arm 26 and reed 54 of nozzle assembly 10.

A high young's modulus dielectric layer 138 is deposited. Layer 138 is formed by depositing 0.2 microns of silicon nitride or aluminum nitride at a temperature below the hard bake temperature of

sacrificial layers

108, 112, 120, and 128.

Layer 138 is then anisotropically plasma etched to a depth of 0.35 microns as shown in fig. 8 p. This etch is intended to remove the dielectric layer from all surfaces except the sidewalls of dielectric layer 132 and sacrificial layer 134. This step creates a nozzle rim 36 around the nozzle opening 24, said nozzle rim 36 "digging" into the meniscus of ink, as previously described.

An Ultraviolet (UV) release tape 140 is applied. A 4 micron resist was spin coated on the back of the silicon wafer 16. Wafer 160 is exposed to mask 142 to bake etch wafer 16 to define ink feed channels 48. The resist is then stripped from the wafer 16.

Another Ultraviolet (UV) release tape (not shown) is applied to the back of the wafer 16 and the release tape 140 is then removed. The

sacrificial layers

108, 112, 120, 128 and 134 are stripped in an oxygen plasma to provide the finished nozzle assembly 10 as shown in fig. 8r and 9 r. For ease of reference, the reference numerals identifying the relevant portions of the nozzle assembly 10 shown in both figures are the same as in fig. 1. Fig. 11 and 12 show a process for manufacturing a nozzle assembly according to the process described in fig. 8 and 9, with reference numerals corresponding to those in fig. 2 to 4.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The described embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. An apertured nozzle guard for an ink jet printer printhead, said printhead including an array of nozzles for ejecting colorant onto a print substrate,

the nozzle guard is suitably positioned on the printhead such that the nozzle guard extends over the exterior of the nozzle to prevent damaging contact with the nozzle while allowing the colorant ejected from the nozzle to pass through the aperture and onto a print substrate; the nozzle guard includes:

an outer surface, said outer surface facing said media in operation;

the outer surface has a groove that individually mates with each of the apertures to prevent debris carried by the blade from clogging the apertures.

2. A nozzle guard according to claim 1 wherein the outer surface further comprises a guide ridge in each recess, the guide ridge being arranged to engage the wiper blade before the wiper blade passes over an aperture which mates with the recess.

3. A nozzle guard according to claim 2 wherein the guide ridge is arcuate and is positioned relative to the direction of travel of the wiper blade to direct residual material away from the aperture and to the edge of the recess.

4. The nozzle guard of claim 1, further comprising a fluid inlet for directing fluid over the nozzle array and directing the fluid out through the channel to prevent foreign particles from collecting on the nozzle array.

5. A nozzle guard according to claim 4 further comprising a pair of integrally formed and spaced apart support members, one of the pair of support members being provided at each end of the nozzle guard.

6. A nozzle guard according to claim 5 wherein the fluid inlet is provided in one of the support elements.

7. A nozzle guard according to claim 6 wherein the fluid inlet is provided in a support element remote from the connection pads of the nozzle array.

8. A nozzle guard according to claim 2 wherein the outer surface is planar except for the groove and the guide ridge.

9. A nozzle guard according to claim 1, wherein the guard is made of silicon.